W32.Netsky@mm Removal Tool

Symantec Security Response has developed a removal tool to clean the infections of the following variants of the Netsky worm:

W32.Netsky.B@mm

W32.Netsky.C@mm

W32.Netsky.D@mm

W32.Netsky.E@mm

W32.Netsky.K@mm

W32.Netsky.P@mm

W32.Netsky.Q@mm

W32.Netsky.S@mm

W32.Netsky.T@mm

W32.Netsky.X@mm

W32.Netsky.Y@mm

W32.Netsky.Z@mm

W32.Netsky.AB@mm

Note: Misleading Applications, also known as Rogue Security Software, are fake antivirus programs that display fake virus infection alerts in order to trick users into downloading or paying for the application. Two commonly reported fake infections are “Worm.Win32.Netsky” and “Win32.Netsky.Q”.

While similar to the name of the threat in this writeup, these fake detections are not related, and running the removal tool will report that no instances of the threat were found on your computer. For more information about Misleading Applications, see the recent Symantec Report on Rogue Security Software.

What the tool does The W32.Netsky@mm Removal Tool does the following:

Terminate the W32.Netsky@mm viral processes.

Delete the W32.Netsky@mm files

Delete the registry values that the worms add

Available command-line switches for this tool

SwitchesThe following switches are designed for use by network administrators:/HELP, /H, /? Displays the help message.

/NOFIXREG Disables the registry repair (We do not recommend using this switch).

/SILENT, /S Enables the silent mode.

/LOG=[PATH NAME] Creates a log file where [PATH NAME] is the location in which to store the tool's output. By default, this switch creates the log file, FxNetsky.log, in the same folder from which the removal tool was executed.

/MAPPED Scans the mapped network drives (We do not recommend using this switch. See the following Note).

/START Forces the tool to immediately start scanning.

/EXCLUDE=[PATH] Excludes the specified [PATH] from scanning (We do not recommend using this switch. See the following Note).

/NOFILESCAN Prevents the scanning of the file system.

Important: Using the /MAPPED switch does not ensure the complete removal of the virus on the remote computer, because:

The scanning of the mapped drives scans only the mapped folders. This may not include all the folders on the remote computer, which can lead to missed detections.

If a viral file is detected on the mapped drive, the removal will fail if a program on the remote computer uses this file.

Therefore, you should run the tool on every computer.

The /EXCLUDE switch will only work with one path, not multiple. An alternative is the /NOFILESCAN switch followed by a manual scan with AntiVirus. This will let the tool alter the registry. Then, scan the computer with AntiVirus and with the current virus definitions. You should be able to clean the file system after completing these steps.

The following example command line can be used to exclude a single drive:

Note: The name of the log file can be whatever you select. The name listed is for the sole purpose of this example.

How to download and run the tool

Important: You must have administrative rights to run this tool on Windows NT 4.0, Windows 2000, or Windows XP.

Note for network administrators: For network administrators. If you are running MS Exchange 2000 Server, we recommend that you exclude the M drive from the scan by running the tool from a command line with the Exclude switch. For more information, read the Microsoft knowledge base article, XADM: Do Not Back Up or Scan Exchange 2000 Drive M (Article 298924).

Save the file to a convenient location, such as your downloads folder or the Windows desktop, or removable media known to be uninfected.

Optional: To check the authenticity of the digital signature, refer to the "Digital signature" section later in this writeup.

Note: If you are sure that you are downloading this tool from the Security Response Web site, you can skip this step. If you are not sure, or are a network administrator and need to authenticate the files before deployment, follow the steps in the "Digital signature" section before proceeding with step 4.

Close all the running programs before running the tool.

If you are on a network or if you have a full-time connection to the Internet, disconnect the computer from the network and the Internet.

If you are running Windows Me or XP, then disable System Restore. Refer to the "System Restore option in Windows Me/XP" section later in this writeup for further details.

Caution: If you are running Windows Me/XP, we strongly recommend that you do not skip this step.

Download and save the Chktrust.exe file to the same folder in which you saved the removal tool.

Note: Most of the following steps are done at a command prompt. If you downloaded the removal tool to the Windows desktop, it will be easier if you first move the tool to the root of the C drive. Then save the Chktrust.exe file to the root of C as well.

(Step 3 to assume that both the removal tool and Chktrust.exe are in the root of the C drive.)

Click Start > Run.

Type one of the following:Windows 95/98/Me:command

Windows NT/2000/XP:cmd

Click OK.

In the command window, type the following, pressing Enter after typing each line:

cd\cd downloadschktrust -i FxNetsky.exe

You should see one of the following messages, depending on your operating system:

Windows XP SP2:The Trust Validation Utility window will appear.

Under Publisher, click the Symantec Corporation link. The Digital Signature Details appears.Verify the contents of the following fields to ensure that the tool is authentic:

Name: Symantec CorporationSigning Time: Friday, April 04, 2008 4:53:41 AMAll other operating systems:You should see the following message:

Do you want to install and run "W32.Netsky Removal Tool" signed on 04/04/08 04:53:41 AM PDT and distributed by Symantec Corporation?

Notes:The date and time in the digital signature above are based on Pacific time. They will be adjusted your computer's time zone and Regional Options settings.

If you are using Daylight Saving time, the displayed time will be exactly one hour earlier.

If this dialog box does not appear, there are two possible reasons:

The tool is not from Symantec: Unless you are sure that the tool is legitimate and that you downloaded it from the legitimate Symantec Web site, you should not run it.

Type exit, and then press Enter. (This will close the MS-DOS session.)

System Restore option in Windows Me/XP Users of Windows Me and Windows XP should temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file onto your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles: